Update copyright

compositor/WingpanelManager/FocusManager.vala

@@ -1,23 +1,9 @@
 /*
- * Copyright (c) 2011-2015 Wingpanel Developers (http://launchpad.net/wingpanel)
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public
- * License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public
- * License along with this program; if not, write to the
- * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
- * Boston, MA 02110-1301 USA.
+ * Copyright 2024 elementary, Inc. (https://elementary.io)
+ * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
- public class GreeterCompositor.FocusManager : GLib.Object {
+public class GreeterCompositor.FocusManager : GLib.Object {
     private unowned Meta.Display display;
     private unowned Meta.Workspace? current_workspace = null;
     private unowned Meta.Window? last_focused_window = null;